Sunday, February 3, 2008

What causes Congenital Heart Defects?

Taken From Mended Little Hearts website.

In most cases, scientists do not know what makes a baby's heart develop abnormally. Both genetic and environmental factors appear to play roles.

Among the few environmental factors known to contribute to congenital heart defects are a virus and certain drugs. Women who contract rubella (German measles) during the first three months of pregnancy have a high risk of having a baby with a heart defect. Other viral infections also may contribute.

Certain medications also increase the risk. These include the acne medication Accutane, lithium (used to treat certain forms of mental illness) and, possibly, certain anti-seizure medications. Drinking alcohol in pregnancy also can increase the risk of heart defects—babies with fetal alcohol syndrome (FAS) often have them. Studies also suggest that use of cocaine in pregnancy increases the risk of these birth defects.

Certain chronic illnesses in the mother also can increase the risk of heart defects. For example, women with diabetes are at increased risk of having a baby with a heart defect, although this risk can be reduced or eliminated if the diabetes is closely controlled, starting before pregnancy. Women with an inborn error of body chemistry called phenylketonuria (PKU) also are at high risk of having a baby with a heart defect, unless they follow a special diet before pregnancy and during the first trimester. Several studies suggest that women who do not consume enough of the B vitamin folic acid before and during the early weeks of pregnancy are at increased risk of having a baby with a heart defect.

While most families have no more than one child with a heart defect, these malformations are more likely to occur in siblings or offspring of people who have heart defects than in unaffected families. This fact has long suggested that genetics plays a role in heart defects, at least in those families. In fact, scientists have recently discovered more than 100 mutations (changes) in more than a dozen genes that directly impair the heart. Many of these mutations cause cardiomyopathy (enlargement of the heart) or heart rhythm disturbances that can be fatal in childhood, adolescence or adulthood.

However, scientists also have pinpointed several mutations that affect the formation of the heart, leading to congenital heart malformations. For example, in 1999 a March of Dimes grantee at the University of Texas Southwestern Medical Center in Dallas discovered a gene that appears to contribute to a common, important group of malformations affecting the heart’s outflow tract and the blood vessels arising from it. Researchers at Harvard Medical School identified a gene responsible for the heart defect called atrial septal defect (a hole between the upper chambers of the heart) in four families with multiple members affected by heart disease. The same researchers also identified another gene mutation that causes atrial septal defects accompanied by arm and hand malformations (Holt-Oram syndrome).

Researchers appear to be on the brink of discovering the genes that underlie numerous heart defects. They have recently identified several genes that direct development of the embryonic heart in mice. This should greatly improve our understanding of these genes’ human counterparts—and possibly lead to ways to prevent the various heart defects that mutations of those genes may cause.

Heart defects also can be part of a wider pattern of birth defects. For example, more than one-third of children with the chromosomal abnormality Down syndrome (characterized by mental retardation and physical birth defects) have heart defects, as do about a quarter of girls with another chromosomal abnormality called Turner syndrome (short stature, lack of sexual development and other problems). In fact, approximately 10 percent of children with heart defects have a chromosomal abnormality. Children with Down, Turner and certain other chromosomal abnormalities should be routinely evaluated for heart defects. Heart defects also are common in children with a variety of inherited disorders, including: Noonan (short stature, learning disabilities), Alagille (liver and other problems), Marfan (skeletal and eye defects) and Williams (mental retardation) syndromes.


Anonymous said...

Hi, my daughter was diagnosed with heart murmmer when she was 4 years old.
They did an heart echo and found out that she has an suboartic membrane. My daughter is 8 years old now, and ever since we have been doing yearly check ups and echos and everything looked the same until last week the doctor gave us the bad news that her membrane has gotten thicker and the numbers has changed from 20 somthing to 60 something. They are talking it over with other heart specialists to see if she needs a surgery. As a mother, I am so devastated that i do not know what i am doing anymore. Any advice from anyone would be great. Thank you Shadi

indah Tagor said...

I have son with CHD, thanks for the information.